1. Field of the Invention
The present invention relates generally to a lock slider for a slide fastener of the type including a mechanism capable of manually or automatically locking the slider in position on a slide fastener, and more particularly to such a lock slider which is particularly suitable for use in a slide fastener of the so-called "concealed" type including fastener tapes used with their fastener element attaching portions being disposed on a backside of a garment.
2. Description of the Prior Art
One known lock slider for a slide fastener of the type is disclosed in Japanese Utility Model Publication No. SHO 63-5533. As shown in FIG. 7, the disclosed lock slider includes a land 20 projecting centrally from the interior surface of an upper wing 5' and extending longitudinally from a guide post 7' toward a rear end 8' of the upper wing 5' for forcing down fastener elements of the slide fastener, and an aperture 13' located at one side of the land 20 for the passage therethrough of a locking pawl.
FIG. 8 shows another known lock slider disclosed in Japanese Patent Laid-open Publication No. HEI 5-305001. The disclosed lock slider is used in a concealed slide fastener and includes a straight ridge 21 of a semi-circular cross-section projecting centrally from the interior surface of an upper wing 5' and extending longitudinally from a guide post 7' toward a rear end of the upper wing 5' for forcing down fastener elements E of the fastener, a pair of lands 22, 22 disposed one on each side of the ridge 21 for pressure engagement with the front side of fastener tapes T to which the fastener elements E are attached by sewing threads S, and an aperture 13' located at an intermediate portion of the lands 22 and the ridge 21 for the passage therethrough of a locking pawl 4'.
Still another example of known lock slider, disclosed in Japanese Patent Laid-open Publication No. SHO 58-7203, includes, as shown here in FIG. 9, a ridge 23 projecting centrally from the interior surface of a planar lower wing 6' and extending longitudinally from the guide post 7' toward a rear end of the lower wing 6', and a pair of furrows 24, 24 disposed one on each side of the ridge 23 for allowing coupling elements E and inner longitudinal tape edge portions to be displaced into the furrows 24 so as to facilitate correction of longitudinal mismatch of opposite fastener tapes T.
The first-mentioned known lock slide-fastener slider has a drawback that the land 20 provided for forcing down the fastener elements and not for spreading open the inner longitudinal edges of the fastener tapes. Therefore, since a peripheral edge of the land 20 is beveled or rounded, the land 20 can readily allow the fastener tapes to lean over the land 20. Thus, the land 20 cannot perform a sufficient spreading of the closely abutting inner longitudinal edges of the fastener tapes. Another drawback is that since the aperture 13' is laterally off the land 20, the locking pawl can not have interlocking engagement with the fastener elements reliably, failing to achieve the prescribed locking function.
According to the second-mentioned known lock slide-fastener slider, the ridge 21 for forcing down the fastener elements E is disposed on the interior surface of the upper wing and extending longitudinally of the upper wing 5', and the lands 22 adapted to be pressed against the front side of the fastener tapes T are disposed on opposite sides of the ridge 21. The lock slider thus constructed also has no function of spreading open the closely abutting inner longitudinal edges of the fastener tapes T and hence the locking pawl 4' is unable to engage with the fastener elements E reliably and an effectual locking function cannot be performed.
In the third-mentioned known lock slide-fastener slider, the furrows 24 are provided in the interior surface of the lower wing 6' on opposite sides of the central ridge 23 for facilitating correction of longitudinal deviation or mismatch of the opposite fastener stringers of the slide fastener. In order to release interlocking engagement between the opposite rows of fastener elements E, the furrows 24 must provide a great space. Therefore, this construction cannot be applied to a slider of the type wherein a locking pawl has interlocking engagement with the fastener elements E while spreading open the closely abutting inner longitudinal edges of the fastener tapes T.